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Updated the thread_pool example so that it mentions the new futures support.

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extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402674
This commit is contained in:
Davis King 2008-11-28 01:33:18 +00:00
parent 4d47d3d356
commit 0270e5ffa6
1 changed files with 43 additions and 3 deletions
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46
examples/thread_pool_ex.cpp
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@ -34,7 +34,8 @@ class test
/*
The thread_pool accepts "tasks" from the user and schedules them
for execution in one of its threads when one becomes available. Each
task is just a request to call a member function on a particular object.
task is just a request to call a member function on a particular object
(or if you use futures you may make tasks that call global functions).
So here we create a class called test with a few member functions which
we will have the thread pool call as tasks.
*/
@ -46,7 +47,7 @@ public:
// Here we ask the thread pool to call this->subtask() three different times
// with different arguments. Note that calls to add_task() will return
// immediately if there is an available thread to hand the task off to, however,
// immediately if there is an available thread to hand the task off to. However,
// if there isn't a thread ready then add_task blocks until there is such a thread.
// Also note that since task_0() is executed within the thread pool (see main() below)
// calls to add_task() will execute the requested task within the calling thread
@ -81,6 +82,18 @@ public:
// ----------------------------------------------------------------------------------------
void add (
long a,
long b,
long& result
)
{
dlib::sleep(400);
result = a + b;
}
// ----------------------------------------------------------------------------------------
int main()
{
// tell the logger to print out everything
@ -115,6 +128,30 @@ int main()
dlog << LINFO << "all tasks finished";
// The thread pool also allows you to use futures to pass arbitrary objects into the tasks.
// For example:
future<long> n1, n2, result;
n1 = 3;
n2 = 4;
// add a task that is supposed to go call add(n1, n2, result);
tp.add_task(add, n1, n2, result);
// This line will wait for the task in the thread pool to finish and when it does
// result will return the integer it contains. In this case r will be assigned a value of 7.
long r = result;
// print out the result
dlog << LINFO << "result = " << r;
// We can also use futures with member functions like so:
tp.add_task(a, &test::task_1, n1, n2);
// and we can still wait for tasks like so:
tp.wait_for_all_tasks();
dlog << LINFO << "all tasks using futures finished";
/* A possible run of this program might produce the following output (the first column is
the time the log message occurred and the value in [] is the thread id for the thread
that generated the log message):
@ -135,7 +172,10 @@ int main()
901 INFO [3] main: task_1 end: 12, 13
1101 INFO [2] main: task_1 end: 14, 15
1101 INFO [0] main: all tasks finished
1503 INFO [0] main: result = 7
1503 INFO [3] main: task_1 start: 3, 4
2203 INFO [3] main: task_1 end: 3, 4
2203 INFO [0] main: all tasks using futures finished
*/
}